[src/trunk]: src/sys/kern Christos was worried about clrbits() being called w...

[dsl <dsl%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/22e8e05b0138
branches:  trunk
changeset: 749031:22e8e05b0138
user:      dsl <dsl%NetBSD.org@localhost>
date:      Sat Nov 14 13:18:41 2009 +0000

description:
Christos was worried about clrbits() being called with a length of zero.
This can't happen, but rework so it doesn't matter.
Remove 'optimisation' for length 1, that doesn't happen often enough.

diffstat:

 sys/kern/tty_subr.c |  38 +++++++++++++++++---------------------
 1 files changed, 17 insertions(+), 21 deletions(-)

diffs (66 lines):

diff -r 3a5eed78fb64 -r 22e8e05b0138 sys/kern/tty_subr.c
--- a/sys/kern/tty_subr.c       Sat Nov 14 10:37:27 2009 +0000
+++ b/sys/kern/tty_subr.c       Sat Nov 14 13:18:41 2009 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tty_subr.c,v 1.38 2009/11/13 19:15:24 dsl Exp $        */
+/*     $NetBSD: tty_subr.c,v 1.39 2009/11/14 13:18:41 dsl Exp $        */
 
 /*
  * Copyright (c) 1993, 1994 Theo de Raadt
@@ -29,7 +29,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tty_subr.c,v 1.38 2009/11/13 19:15:24 dsl Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tty_subr.c,v 1.39 2009/11/14 13:18:41 dsl Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -303,32 +303,28 @@
 static void
 clrbits(u_char *cp, unsigned int off, unsigned int len)
 {
-       unsigned int sby, sbi, eby, ebi;
-       unsigned int i;
-       u_char mask;
-
-       if (len==1) {
-               clrbit(cp, off);
-               return;
-       }
+       unsigned int sbi, ebi;
+       u_char *scp, *ecp;
+       unsigned int end;
+       unsigned char mask;
 
-       len--;
-       sby = off / NBBY;
+       scp = cp + off / NBBY;
        sbi = off % NBBY;
-       eby = (off+len) / NBBY;
-       ebi = (off+len) % NBBY + 1;
-       if (sby == eby) {
-               mask = ((1 << (ebi - sbi)) - 1) << sbi;
-               cp[sby] &= ~mask;
+       end = off + len + NBBY - 1;
+       ecp = cp + end / NBBY - 1;
+       ebi = end % NBBY + 1;
+       if (scp >= ecp) {
+               mask = ((1 << len) - 1) << sbi;
+               *scp &= ~mask;
        } else {
                mask = (1 << sbi) - 1;
-               cp[sby++] &= mask;
+               *scp++ &= mask;
 
                mask = (1 << ebi) - 1;
-               cp[eby] &= ~mask;
+               *ecp &= ~mask;
 
-               for (i = sby; i < eby; i++)
-                       cp[i] = 0x00;
+               while (scp < ecp)
+                       *scp++ = 0x00;
        }
 }
 #endif